First human embryonic stem cell trial
Let me give you two scenarios. First the wildly optimistic: that thirty years from now we will look back on today as one of the most significant in the history of modern medicine; the day everything began to change. The second is pessimistic: that in the near future we will see that embryonic stem cells did not live up to the hype, dashing the hopes of patients.
The truth is no-one can be sure which of the above will come true, or something more prosaic but still useful in terms of tackling disease.
So much has been written about embryonic stem cells that it seems hard to fathom that the first officially approved human trial is only now underway. To supporters they represent the best hope for repairing organs and curing disease.
The dream is that - many years from now - you will be able to use stem cells to repair a damaged heart, cure diabetes and restore function to patients with spinal cord injury.
We know that adult stem cells work, for example bone marrow transplantation. There have been other transplant techniques using adult stem cells.
But until now, human embryonic stem cells had never been injected into a patient - at least not in a licensed trial.
Now, Geron, a biotech firm in California has announced that it has begun a safety trial where embryonic stem cells will be injected into half a dozed patients who recently suffered spinal cord injuries. The first patient, whose details have not been released, has already had the treatment. The amount of cells injected will have been tiny because this "first in man" trial is simply there to test safety. Only if no harm is done will increasingly bigger doses be given, and only then will scientists know whether it can help restore some function.
In animal trials, paralysed rats did regain movement. But, as many trials have shown in the past, that does not assure success in humans.
Not even the most enthusiastic supporters of this research are suggesting that paralysed patients will be walking again as a result of this study. But even a minor improvement in function would be of huge benefit.
Professor Chris Mason from University College London said this is an exciting moment: "It's important because these are embryonic stem cells - the most potent we have available for therapy. They can make all the 200 cell types in the body and they can make them in quantity. If this therapy is successful, and that might take five to ten years, then we will be able to manufacture it in the scale we need."
The trial will spark controversy in the United States. Critics argue that it is wrong to use cells derived from human embryos because they would have been destroyed in the process, when they are still smaller than a pinhead. In one of his first actions as President, Barack Obama lifted many restrictions on federal funding of embryonic stem cell research when he came to office last year. There is currently a legal dispute over federal funding which is going through the US Court of Appeal.